<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>固定定位</title>
    <style>
        .box{
            width: 70%;
            height: auto;

            position: relative;
            margin: 15px auto;
        }

        #back{
            width: 50px;
            height: 120px;

            position: fixed;
            bottom: 0;
            right: 0;
            text-align: center;
            padding-top: 50px;
        }
    </style>
</head>
<body>
    <!-- 锚点 -->
    <a id="top"></a>
    <div class="box">
        <img src="./img/box.png" alt="">
    </div>
    <div id="back"><img src=".\ad-l.png"></img></div>
    <div id="back"><img src=".\ad-r.png"></img></div>
</body>
</html>